(i) Field of the Invention
This invention relates to a method for producing a chemical mechanical polishing pad.
(ii) Description of the Related Art
In production of semiconductor devices or the like in recent years, chemical mechanical polishing (generally abbreviated as “CMP”) is often used as a polishing method capable of forming a surface having excellent flatness. As for this chemical mechanical polishing, it is known that polishing results depend largely on the characteristics and properties of a chemical mechanical polishing pad to be used. The polishing results include, for example, a removal rate, and scratches and in-plane uniformity on a polished surface.
As the chemical mechanical polishing pad, a variety of polishing pads have been proposed.
For example, in Japanese Patent Application Laid-Open Nos. 8-500622 and 2000-34416, materials constituting chemical mechanical polishing pads are studied. Further, in Japanese Patent Application Laid-Open No. 11-70463, for example, design of grooves on a surface (polishing surface) of a pad is studied. These chemical mechanical polishing pads mainly comprise a cross-linked polymer and pores or water-soluble particles dispersed in the polymer. As the chemical mechanical polishing pads, a chemical mechanical polishing pad comprising a thermoplastic polyurethane resin as a cross-linked polymer and pores dispersed in the resin is disclosed in Japanese Patent Application Laid-Open No. 8-500622, and a chemical mechanical polishing pad comprising 1,2-polybutadiene as a cross-linked polymer and water-soluble particles dispersed in the polymer is disclosed in Japanese Patent Application Laid-Open No. 2004-327974, for example.
The above chemical mechanical polishing pad comprising a thermoplastic polyurethane resin and pores is generally produced by cutting a polishing pad of desired thickness and shape out of a foamed polyurethane block prepared in advance. Production of this foamed polyurethane block requires processing at a temperature of about 150° C. for 1 to 4 hours, for example, and a cutting process for shaping the block into the shape of the polishing pad is further required. Thus, productivity of the polishing pad is not high.
Meanwhile, the above chemical mechanical polishing pad comprising 1,2-polybutadiene and water-soluble particles dispersed in the polymer is an excellent polishing pad free of problems in polishing performance of the chemical mechanical polishing pad comprising a thermoplastic polyurethane resin and pores dispersed in the resin and can be produced by, for example, heating a raw material composition for the pad which comprises 1,2-polybutadiene, water-soluble particles and a peroxide in a mold to cross-link the 1,2-polybutadiene component with the peroxide. In this case, the heating treatment must be carried out at a temperature of 170 to 180° C. for 10 to 20 minutes per polishing pad. Thus, productivity of the polishing pad is also not so high. Further, in the case of the chemical mechanical polishing pad comprising 1,2-polybutadiene and water-soluble particles dispersed in the polymer, a phenomenon is seen that although it shows an excellent initial removal rate immediately after its production, the removal rate gradually decreases as it chemical-mechanical-polishes a number of objects to be polished successively. Further, it is pointed out that the removal rate of polishing pad of this type shows rather strong temperature dependency.